Appearance
Because of their globose shape, adults resemble those of Sperchopsis tessellata, which occur in a similar habitat. Adults of S. tessellata are brown above instead of rusty-olive, and have alternate elytral intervals raised to form low ridges; elytra of H. melaenus adults are smooth.Naming
Hydrobius melaenus (Germar, 1824)Distribution
Canada: Ontario to Nova ScotiaUS: North Carolina to Indiana to Wisconsin
Habitat
Adults and larvae were collected from under hanks of small, spring-fed streams.Reproduction
Adults occurred 9 January-26 November, but were scarce in June (4%) and not found in July. Teneral adults were found 10-26 August, and larvae occurred from October-July. Adults and larvae overwinter under banks of spring-fed streams, with adults probably mating and ovipositing in spring and then apparently dying. Occurrence ofsmall and large larvae together, and larger larvae from late October-July, suggest slow development in the cold habitat along spring-fed streams, and a semivoltine life cycle.References:
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Hilsenhoff, William L. 1995. "Aquatic Hydrophilidae and Hydraenidae of Wisconsin (Coleoptera). II. Distribution, Habitat, Life Cycle and Identification of Species of Hydrobiini and Hydrophilini (Hydrophiudae: Hydrophilinae)," The Great Lakes Entomologist, vol 28 (2) Available at: https://scholar.valpo.edu/tgle/vol28/iss2/1